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Cardiac troponin I (cTnI) and cardiac troponin T (cTnT) determinations are fixtures in clinical practice and research. Cardiac troponin testing has been the standard of practice for the diagnosis of acute myocardial infarction (AMI), early rule-out, risk stratification, and outcomes assessment in patients presenting with acute coronary syndrome (ACS) and non-ACS myocardial injury. We recognize from reading the literature over the past several years how poorly understood the analytical characteristics are for cTnI and cTnT assays by laboratorians, clinicians, and scientists who use these assays. The purposes of this mini-review are (a) to define limit of blank, limit of detection, limit of quantification, and imprecision, (b) overview the analytical characteristics of the existing cardiac troponin assays, (c) recommend approaches to define a healthy (normal) reference population for determining the 99th percentile and the appropriate statistic to use for this calculation, (d) clarify how an assay becomes designated as \"high sensitivity,\" and (e) provide guidance on determining delta (Δ) change values. This review raises important educational information regarding cTnI and cTnT assays, their 99th percentile upper reference limits (URL) differentiated by sex, and specifically addresses high-sensitivity (hs)-assays used to measure low concentrations. Recommendations are made to help clarify the nomenclature and analytical and clinical characteristics to define hs-assays. The review also identifies challenges for the evolving implementation of hs-assays into clinical practice. It is hoped that with the introduction of these concepts, laboratorians, clinicians and researchers can develop a more unified view of how these assays should be used worldwide.

Abstract Background Many studies have assessed the biological variation (BV) of cardiac-specific troponins (cTn), reporting widely varying within-subject BV (CVI) estimates. The aim of this study was to provide meta-analysis-derived BV estimates for troponin I (cTnI) and troponin T (cTnT) for different sampling intervals and states of health. Methods Relevant studies were identified by a systematic literature search. Studies were classified according to their methodological quality by the Biological Variation Data Critical Appraisal Checklist (BIVAC). Meta-analyses of BIVAC-compliant studies were performed after stratification by cTn isoform, exclusion of results below the limit of detection, states of health, and sampling interval to deliver reference change values (RCV), index of individuality (II) and analytical performance specifications (APS) for these settings. Results Sixteen and 15 studies were identified for cTnI and cTnT, respectively, out of which 6 received a BIVAC grade A. Five studies had applied contemporary cTnI assays, but none contemporary cTnT. High-sensitivity (hs-) cTnI and cTnT delivered similar estimates in all settings. Long-term CVI estimates (15.1; 11.3%) derived from healthy individuals were higher than short-term (4.3%; 5.3%) for hs-cTnI and hs-cTnT, respectively, although confidence intervals overlapped. Estimates derived from diseased subjects were similar to estimates in healthy individuals for all settings. Conclusions This study provides robust estimates for hs-cTnI and hs-cTnT applicable for different clinical settings and states of health, allowing for the use of RCV both to aid in the diagnosis of myocardial injury and for prognosis. BV-based APS appear too strict for some currently available technologies.

Increasing numbers of patients are presenting worldwide to emergency departments with suspected myocardial infarction. The use of point-of-care troponin assays might enable faster decision-making in this high-risk population and reduce the burden on emergency facilities. Here, we evaluate the diagnostic performance of a point-of-care high-sensitivity troponin I assay. We conducted a prospective cohort study including patients presenting to the emergency department with suspected myocardial infarction from July 2013 to July 2016. A diagnostic algorithm for a high-sensitivity troponin I point-of-care assay was developed in a derivation data set with 669 patients and validated in an additional 610 patients. The derived 0/1 h algorithm for the point-of-care assay consisted of an admission troponin I <4 ng/L and a δ from 0 h to 1 h <3 ng/L for rule out and an admission troponin I ≥90 ng/L or a δ from 0 h to 1 h ≥20 ng/L for rule in of non-ST-elevation myocardial infarction. Application to the validation cohort showed a negative predictive value of 99.7% (95% CI, 98.1%-100.0%) and 48.0% of patients ruled out, whereas 14.6% were ruled in with a positive predictive value of 86.5% (95% CI, 77.6%-92.8%). The diagnostic performance of the point-of-care high-sensitivity assay was highly comparable to guideline-recommended use of a laboratory-based high-sensitivity troponin assay. The clinical application of a 0/1 h diagnostic algorithm based on a high-sensitivity troponin I point-of-care assay is safe, and diagnostic performance is comparable to a laboratory-based high-sensitivity troponin I assay.

The universal definition of myocardial infarction (UDMI) standardizes the approach to the diagnosis and management of myocardial infarction. High-sensitivity cardiac troponin testing is recommended because these assays have improved precision at low concentrations, but concerns over specificity may have limited their implementation. We undertook a global survey of 1902 medical centers in 23 countries evenly distributed across 5 continents to assess adoption of key recommendations from the UDMI. Respondents involved in the diagnosis and management of patients with suspected acute coronary syndrome completed a structured telephone questionnaire detailing the primary biomarker, diagnostic thresholds, and clinical pathways used to identify myocardial infarction. Cardiac troponin was the primary diagnostic biomarker at 96% of surveyed sites. Only 41% of centers had adopted high-sensitivity assays, with wide variation from 7% in North America to 60% in Europe. Sites using high-sensitivity troponin more frequently used serial sampling pathways (91% vs 78%) and the 99th percentile diagnostic threshold (74% vs 66%) than sites using previous-generation assays. Furthermore, high-sensitivity institutions more often used earlier serial sampling (≤3 h) and accelerated diagnostic pathways. Fewer than 1 in 5 high-sensitivity sites had adopted sex-specific thresholds (18%). There has been global progress toward the recommendations of the UDMI, particularly in the use of the 99th percentile diagnostic threshold and serial sampling. However, high-sensitivity assays are still used by a minority of sites, and sex-specific thresholds by even fewer. Additional efforts are required to improve risk stratification and diagnosis of patients with myocardial infarction.

BackgroundThe Manchester Acute Coronary Syndromes (MACS) rule and the Troponin-only MACS (T-MACS) rule risk stratify patients with suspected acute coronary syndrome (ACS). This observational study sought to validate and compare the MACS and T-MACS rules for assessment of acute myocardial infarction (AMI).MethodsProspectively collected data from twoEDs in Australia and New Zealand were analysed. Patients were assigned a probability of ACS based on the MACS and T-MACS rules, incorporating high-sensitivity troponin T, heart-type fatty acid-binding protein, ECG results and clinical symptoms. Patients were then deemed very low risk, low risk, intermediate or high risk if their MACS probability was less than 2%, between 2% and 5%, between 5% and 95% and greater than 95%, respectively. The primary endpoint was 30-day diagnosis of AMI. The secondary endpoint was 30-day major adverse cardiac event (MACE) including AMI, revascularisation or coronary stenosis (>70%). Sensitivity, specificity and predictive values were calculated to assess the accuracy of the MACS and T-MACS rules.ResultsOf the 1244 patients, 114 (9.2%) were diagnosed with AMI and 163 (13.1%) with MACE. The MACS and T-MACS rules categorised 133 (10.7%) and 246 (19.8%) patients, respectively, as very low risk and potentially suitable for early discharge from the ED. There was one false negative case for both rules making sensitivity 99.1% (95.2%–100%).ConclusionsMACS and T-MACS accurately risk stratify very low risk patients. The T-MACS rule would allow for more patients to be discharged early. The potential for missed MACE events means that further outpatient testing for coronary artery disease may be required for patients identified as very low risk.

To compare the performance of high-sensitivity cardiac troponin I and T (hs-cTnI; hs-cTnT) in diagnosing obstructive coronary artery disease (CAD 50 ) in patients with suspected chronic coronary syndrome (CCS). A total of 706 patients with suspected CCS, referred for Coronary Computed Tomography Angiography, were included. cTn concentrations were measured using the Singulex hs-cTnI (limit of detection [LoD] 0.08 ng/L) and Roche hs-cTnT (LoD 3 ng/L) assays. Obstructive coronary artery disease (CAD 50 ) was defined as ≥ 50% coronary stenosis. Cardiovascular risk was determined by the NORRISK2-score. Median age of the patients was 65 (range 28–87) years, 35% were women. All patients had hs-cTnI concentrations above the LoD (median 1.9 [Q1-3 1.2–3.6] ng/L), 72% had hs-cTnT above the LoD (median 5 [Q1-3 2–11] ng/L). There was a graded relationship between hs-cTn concentrations and coronary artery calcium. Only hs-cTnI remained associated with CAD 50 in adjusted analyses (OR 1.20 95% Confidence Interval [1.05–1.38]), p  = 0.009). The C-statistics for hs-cTnI and hs-cTnT were 0.65 (95% CI [0.60–0.69]) and 0.60 (0.56–0.64). The highest specificity and negative predictive values for CAD 50 were in the lowest NORRISK2-tertile. hs-cTn concentrations provide diagnostic information in patients with suspected CCS, with superior performance of hs-cTnI compared to hs-cTnT in regard to CAD 50 . The diagnostic performance appeared best in those with low cardiovascular risk.

It has been difficult to establish whether we are limited to the heart muscle cells we are born with or if cardiomyocytes are generated also later in life. We have taken advantage of the integration of carbon-14, generated by nuclear bomb tests during the Cold War, into DNA to establish the age of cardiomyocytes in humans. We report that cardiomyocytes renew, with a gradual decrease from 1% turning over annually at the age of 25 to 0.45% at the age of 75. Fewer than 50% of cardiomyocytes are exchanged during a normal life span. The capacity to generate cardiomyocytes in the adult human heart suggests that it may be rational to work toward the development of therapeutic strategies aimed at stimulating this process in cardiac pathologies.

Abstract Background We assessed the accuracy and clinical effectiveness of high-sensitivity cardiac troponin (hs-cTn) assays for early rule-out of non-ST-segment elevation myocardial infarction (NSTEMI) in adults presenting with acute chest pain. Methods Sixteen databases were searched to September 2019. Review methods followed published guidelines. The bivariate model was used to estimate summary sensitivity and specificity with 95% confidence intervals for meta-analyses involving 4 or more studies, otherwise random-effects logistic regression was used. Results Thirty-seven studies (124 publications) were included in the review. The hs-cTn test strategies evaluated in the included studies were defined by the combination of 4 factors (assay, number of tests, timing of tests, and threshold concentration or change in concentration between tests). Clinical opinion indicated a minimum acceptable sensitivity of 97%. A single test at presentation using a threshold at or near the assay limit of detection could reliably rule-out NSTEMI for a range of hs-cTn assays. Serial testing strategies, which include an immediate rule-out step, increased the proportion ruled out without loss of sensitivity. Finally, serial testing strategies without an immediate rule-out step had excellent sensitivity and specificity, but at the expense of the option for immediate patient discharge. Conclusion Test strategies that comprise an initial rule-out step, based on low hs-cTn concentrations at presentation and a minimum symptom duration, and a second step for those not ruled-out that incorporates a small absolute change in hs-cTn at 1, 2, or 3 hours, produce the highest rule-out rates with a very low risk of missed NSTEMI. PROSPERO registration CRD42019154716

Being a leading cause of death, heart diseases across the globe need special attention to enable early diagnosis. Metal nanoparticle-mediated biosensors are useful clinical tools for the early detection of bio-analytes. The size-dependent surface plasmon resonance (SPR) of metal nanoparticles can be effectively utilized for the same purpose. The early detection of heart diseases can be evaluated by monitoring the troponin level. A copper nanoparticle-mediated troponin biosensor was developed through antibody conjugation for troponin I and troponin T. The copper nanosensor shows a concentration-dependent SPR change towards troponin T and troponin I.